The invention relates to a method for transporting loads in which gripper claws of pivoting gripper arms engage pre-defined connecting regions of the load and, prior to engaging the load, are pivoted out of an initial position into an operating position, and, after the gripper arms have been pivoted into the operating position, gripper pliers are positioned transversely for engaging connecting regions of the load.
The invention further relates to an apparatus for transporting loads, which has gripper claws that are held by pivoting gripper arms, and in which the gripper arms have a plier guide that extends essentially transversely with respect to the pivoting direction of the arms. Gripper pliers can be positioned along this guide for engaging connecting regions of the load.
Apparatuses of this type are configured as load-receiving means, and can be used to grip containers, interchangeable containers, or semitrailers. The apparatus is typically positioned for use with the aid of cranes. The apparatus is usually mounted on "spreaders." Spreaders are provided with twist locks that can be inserted into corner fittings of containers and permit a form-fitting latching with the container. The head girders having twist locks can be telescopic.
In the present case, however, a primary feature is a spreader embodiment in which two folding and pivotable gripper-plier pairs are used to grip interchangeable containers or semitrailers. The gripper pliers are in lateral contact with gripper pockets attached to the loading units (i.e. the containers or semitrailers). The loading units are supported on gripper claws of the gripper pliers, and are fixed solely by friction in the longitudinal direction of the container.
Spreaders having gripper pliers are used in different environments, for example in the area of rail-bound transport of goods in crane facilities of transfer terminals. The gripper pliers are typically seated in pendulum fashion in the operating position, and can pivot out in opposite directions by about.+-.10 from the operating position . Under the effect of horizontal accelerations, the cargo can consequently swing out in both the transport direction and transversely thereto, so horizontal accelerations of up to about 0.5 m/sec.sup.2 can be tolerated without problems.
The pendulum movements resulting from this swinging out, however, impede automatic operation of the crane, both during acceleration and slowing. The effect of wind, particularly wind gusts, can cause deviations in position. Likewise, swinging may also occur due to horizontal accelerations. This type of deviation from the desired position can only be compensated by complicated control algorithms that increase the outlay for regulating technology and machinery, increase the time requirement for positioning procedures and reduce the operational capacity due to the necessary settling times.
The known apparatuses and methods are inadequately suited for reliably preventing off-centering of loading units relative to the gripper device during gripper-plier operation, because the forces acting in the longitudinal direction can only be introduced into the gripper arms by the above mentioned frictional connection. One problem that may occur is that the center of gravity of the loading units can be off-center. Under these conditions, different frictional forces occur in the region of the gripper pliers, so the supported weight is asymmetrically distributed onto the gripper pliers as a function of the fixed position of the center of gravity.